Cardiovascular disease, the hallmark of many diseases, is a leading process of death worldwide.
Myocardial or cerebral infarction exemplifies a complex clinical syndrome that results from a harmful and damaging, permanent or transitional, myocardial ischemia. This is usually caused by coronary/cerebral artery occlusion, resulting in an imbalance between oxygen supply and demand.
Tissue damages depend on the duration of ischemia. For ischemia as short as 5 minutes, the ischemic tissue ultimately recovers after reperfusion, without infarction symptoms or lethal consequences. However, ischemia of significant duration leads to infarction and inflammatory reaction. Indeed, infarction is associated with an inflammatory reaction, which is a prerequisite of healing and scar formation [Entman M. L. et al., 1994 and Mehta J. L. et al., 1999]. This response is amplified in terms of magnitude and duration when the ischemic tissue is reperfused.
This response is multiphasic: initial ischemia induces necrosis, formation of free radical oxygen species, complement activation, and a cytokine cascade initiated by TNF-alpha release. Reperfusion phase of the infracted area is associated with an increased and accelerated inflammatory reaction responsible for leucocytes recruitment at the site of ischemia. Recruited leucocytes also participate to an in situ and systemic release of inflammatory mediators, leading in fine to a hyperactivated inflammatory state, responsible for pathophysiological consequences of infarction.
All the inflammatory mediators have controversial effects. Indeed, infarction physiopathology is balanced between their beneficial and adverse effects. For example, TNF-alpha displays cytoprotective effects during myocardial ischemia, as well as deleterious effects [Harjot K Saini. et al., 2005], depending on time, duration and level of its expression and release. This may explain the complexity of a therapy based on blocking such inflammatory mediators.
Release of mediators of inflammation (cytokines, chemokines, ROS . . . ) and massive leukocyte recruitment play an important role during all stages of the ischemic cascade, from the early damaging events triggered by arterial occlusion to the late regenerative processes underlying post-ischemic tissue-repair. Many therapeutic strategies targeting this inflammatory response failed to demonstrate any efficacy. It seems now obvious that it is worth tempting to act on amplification loops rather than on individual ischemia-induced inflammatory mediator.
Atherosclerosis gives rise to cerebrovascular disease and coronary artery disease through a slowly progressing lesion formation and luminal narrowing of arteries. Upon plaque rupture and thrombosis, these most common forms of cardiovascular disease manifest as acute coronary syndrome (ACS), myocardial infarction or stroke. Human and animal studies have established that atherosclerosis is driven by a chronic inflammatory process within the arterial wall initiated mainly in response to endogenously modified structures, particularly oxidized lipoproteins that stimulate both innate and adaptive immune responses. The innate response is instigated by the activation of both vascular cells and monocytes/macrophages, subsequently an adaptive immune response develops against an array of potential antigens presented to effector T lymphocytes by antigen-presenting cells [Ait-Oufella H et al., 2011]. Genetically modified mouse models taught us that circulating monocytes were recruited into the vascular wall by chemokines and then become macrophages and lipid-loaded foam cells. Intima macrophages promote plaque development through cytokine release, inflammation amplification and plaque destabilization through protease production and apoptosis accumulation [Libby P. 2002].
Monocytes/macrophages are stimulated by several mediators named PAMPs (for Pathogen Associated Molecular Patterns) that interact with PRRs (for Pathogen Recognition Receptors). Several PRRs are implicated in the physiopathology in atherosclerosis. For example, Toll-like receptors are expressed in human and animal atherosclerotic lesions. TLR inhibition reduces atherosclerosis development in mice suggesting that targeting such pathways could be atheroprotective [Bjorkbacka H et al., 2004].
Recently, a new family of receptors expressed on myeloid cells has been described: Triggering Receptors Expressed on Myeloid cells (TREMs). Among this family, TREM-1 is expressed on monocytes/macrophages and neutrophils. TREM-1 activation leads to cytokines and chemokines production (TNF-α, IL-6, IL-8, MCP-1 and -3, MIP-1α . . . ) along with rapid neutrophil degranulation and oxidative burst [Radsak M P et al., 2004 and Hara H, et al., 2009].
The TREM-1 function is to modulate/amplify rather than to activate/initiate inflammation by synergizing with TLRs in order to trigger an exuberant immune response. Pathophysiological role of TREM-1 was firstly identified during infectious diseases. TREM-1 is known to play a crucial role during aseptic inflammation, both acute (mesenteric ischemia-reperfusion, hemorrhagic choc, pancreatitis . . . ) and chronic (Inflammatory Bowel Diseases, Rheumatic diseases . . . ).
TLT-1 (Trem-Like Transcript-1) is a member of TREM family but exclusively found in megakaryocytes and platelets. TLT-1 was first identified to play a role during platelet aggregation by linking fibrinogen and stabilizing platelet aggregate. But new findings from the inventor's laboratory on TLT-1, soluble TLT-1 and sTLT-1-derived polypeptides have shown that TLT-1 plays a role during inflammation by specifically inhibiting TREM-1 [Derive M et al., 2012, WO2010/124685].
Washington et al. described that TLT-1 plays a protective role during inflammation by facilitating platelet aggregation at sites of vascular injury (Washington et al. J Clin Invest. 2009).
Since it is known that platelet aggregation is associated with a worst outcome during cardiovascular diseases (e.g. myocardial infarction and atherosclerosis), it was surprising to find that TLT-1-derived peptides have a therapeutic effect on cardiovascular diseases.
The inventors herein describe that TREM-1 is expressed 1) by the endothelial cells from aorta, mesenteric artery, and microvascular cells 2) by myocardial tissue and that its expression is up-regulated in infarcted areas following myocardial ischemia (permanent myocardial ischemia and transient myocardial ischemia) 3) by the macrophages recruited into atheromatous plaques.
They also show that both TREM-1 and TLT-1-derived peptides are able to specifically inhibit TREM-1, and decrease TREM-1 associated inflammatory response in myocardial infarction, and atherosclerosis.
As a result, administration of these peptides during acute phase of 2 different models of myocardial ischemia (permanent ischemia and transient ischemia) was responsible for a modulation of in situ inflammatory response and ensuing leucocyte trafficking, thus limiting post-ischemic cardiac remodelling and later stages of disease progression. Indeed, cardiac function was dramatically improved 6 weeks after permanent ischemia as well as transient ischemia (ischemia-reperfusion) event. This translated into survival gain.
They finally demonstrate a role of TREM-1 and TLT-1-derived peptides in reducing the extend of atheromatous plaque formation by specifically inhibiting TREM-1.
Thus, the invention relates to a peptide comprising at least 6 consecutive amino acid selected from the amino acid sequence SEQ ID NO: 2 and a function-conservative variant.
Moreover, the invention relates to a peptide comprising at least 6 consecutive amino acid selected from the amino acid sequence SEQ ID NO: 1 or SEQ ID NO: 2 and a function-conservative variant or an isolated nucleic acid, an expression vector, a host cell according to the invention for use in the treatment of a cardiovascular disease.